Normally on my Mobile (Samsung A51) i choose
“Settings → Connections → Mobile networks → Network operators” there
Select automatically or Select manually
i’m sure that is possible, to write a kotlin app - where i have
a) two Buttons
Button 1 => Select automatically
Button 2 => Select manually
or b) Come directly to the screen “Network operators” (there i can chosse Select automatically or Select manually)
If you are uncertain about the Android APIs to use for your specific task, you are more likely to get a better response on a forum like Stack Overflow.
This forum is specifically for Kotlin. You’ll get better answers elsewhere with questions that are really more Android focused.